Plexiform nerve sheath tumor or vascular malformation—role of advanced MR neurography and diffusion tensor imaging

The authors report a vascular malformation mimicking a plexiform peripheral nerve sheath tumor. Three Tesla magnetic resonance neurography with high-resolution anatomic and advanced functional diffusion tensor imaging was helpful in evaluating full extent of the lesion and characterizing its internal architecture.     

Thoracic outlet syndrome in 3T MR neurography—fibrous bands causing discernible lesions of the lower brachial plexus

Objectives

To investigate whether targeted magnetic resonance neurography (MRN) of the brachial plexus can visualise fibrous bands compressing the brachial plexus and directly detect injury in plexus nerve fascicles.

Methods

High-resolution MRN was employed in 30 patients with clinical suspicion of either true neurogenic thoracic outlet syndrome (TOS) or non-specific TOS. The protocol for the brachial plexus included a SPACE (3D turbo spin echo with variable flip angle) STIR (short tau inversion recovery), a sagittal-oblique T2-weighted (T2W) SPAIR (spectral adiabatic inversion recovery) and a 3D PDW (proton density weighted) SPACE. Images were evaluated for anatomical anomalies compressing the brachial plexus and for abnormal T2W signal within plexus elements. Patients with abnormal MR imaging findings underwent surgical exploration.

Results

Seven out of 30 patients were identified with unambiguous morphological correlates of TOS. These were verified by surgical exploration. Correlates included fibrous bands (n?=?5) and pseudarthrosis or synostosis of ribs (n?=?2). Increased T2W signal was detected within compressed plexus portion (C8 spinal nerve, inferior trunk, or medial cord) and confirmed the diagnosis.

Conclusions

The clinical suspicion of TOS can be diagnostically confirmed by MRN. Entrapment of plexus structures by subtle anatomical anomalies such as fibrous bands can be visualised and relevant compression can be confirmed by increased T2W signal of compromised plexus elements.

Key Points

? MR neurography (MRN) can aid the diagnosis of thoracic outlet syndrome (TOS). ? Identifiable causes of TOS in MRN include fibrous bands and bony anomalies. ? Increased T2W signal within brachial plexus elements indicate relevant nerve compression. ? High positive predictive value allows confident and targeted indication for surgery.     

Evaluation of 100 brain examinations using a 3 Tesla MR-compatible incubator—safety, handling, and image quality

Introduction

Several studies have revealed the importance of brain imaging in term and preterm infants. The aim of this retrospective study was to review safety, handling, and image quality of MR brain imaging using a new 3 Tesla MR-compatible incubator.

Methods

Between 02/2011 and 05/2012 100 brain MRIs (84 infants, mean gestational age 32.2?±?4.7 weeks, mean postmenstrual age at imaging 40.6?±?3.4 weeks) were performed using a 3 Tesla MR-compatible incubator with dedicated, compatible head coil. Seventeen examinations (13 infants, mean gestational age 35.1?±?5.4 weeks, mean postmenstrual age at imaging 47.8?±?7.4 weeks) with a standard head coil served as a control. Image analysis was performed by a neuroradiologist and a pediatric radiologist in consensus.

Results

All but two patients with known apnea were transferred to the MR unit and scanned without problems. Handling was easier and faster with the incubator; relevant motion artifacts (5.9 vs. 10.8 %) and the need for repetitive sedation (43.0 vs. 86.7 %) were reduced. Considering only images not impaired by motion artifacts, image quality (4.8?±?0.4 vs. 4.3?±?0.8, p?=?0.047) and spatial resolution (4.7?±?0.4 vs. 4.2?±?0.6, p?=?0.011) of T2-weighted images were scored significantly higher in patients imaged with the incubator. SNR increased significantly (171.6?±?54.5 vs. 80.5?±?19.8, p?<?0.001) with the use of the incubator.

Conclusion

Infants can benefit from the use of a 3 Tesla MR-compatible incubator because of its safety, easier, and faster handling (compared to standard imaging) and possibility to obtain high-quality MR images even in unstable patients.     

Multidetector CT imaging in mesenteric ischemia—pearls and pitfalls

Mesenteric ischemia is a complex and devastating disease which still remains a diagnostic challenge to the clinicians due to non-specific clinical and laboratory findings. Several imaging features have been described with multidetector computed tomography which allows the diagnosis of mesenteric ischemia with high sensitivity and specificity. However, there are imaging features which overlap with other pathologies including benign inflammation and infection. Knowledge of imaging findings in mesenteric ischemia and its potential mimics is important in early and definitive diagnosis.     

Chemical exchange saturation transfer MR imaging of Parkinson’s disease at 3 Tesla

Objectives

To demonstrate the feasibility of using chemical exchange saturation transfer (CEST) imaging to detect Parkinson’s disease (PD) in patients at 3 Tesla.

Methods

Twenty-seven PD patients (17 men and 10 women; age range, 54–77 years) and 22 age-matched normal controls (13 men and 9 women; age range, 55–73 years) were examined on a 3-Tesla MRI system. Magnetization transfer spectra with 31 different frequency offsets (?6 to 6 ppm) were acquired at two transverse slices of the head, including the basal ganglia and midbrain. One-way analysis of variance tests was used to compare the differences in CEST imaging signals between PD patients and normal controls.

Results

Total CEST signal between the offsets of 0 and 4 ppm in the substantia nigra was significantly lower in PD patients than in normal controls (P?=?0.006), which could be associated with the loss of dopaminergic neurons. Protein-based CEST imaging signals at the offset of 3.5 ppm in the globus pallidus, putamen and caudate were significantly increased in PD patients, compared to normal controls (P?P?=?0.003, P?Conclusions CEST imaging signals could potentially serve as imaging biomarkers to aid in the non-invasive molecular diagnosis of PD.

Key Points

? Total CEST signal in substantia nigra decreased in PD patients ? Protein-based CEST signals in basal ganglia increased in PD patients ? CEST could assist with the non-invasive molecular diagnosis for PD patients     

Endoscopic calcaneoplasty—rationale,surgical technique,and early results: a preliminary report

We present our technique and preliminary results with endoscopic calcaneoplasty in ten patients resistant for conservative therapy for more than 6 months. All patients showed a Haglund spur on radiography; none had a cavovarus deformity. Follow-up ranged from 2 to 12 months (mean 5.2). All patients showed clinical improvement and would undergo for the procedure again. Three showed a good and seven an excellent result in Ogilvie-Harris score. Postoperative radiographic follow-up showed sufficient bone removal in all cases. Surgery lasted on average 46 min (range 28-84). There were no intra- or postoperative complications. Endoscopic calcaneoplasty is an effective minimally invasive treatment option for patients with retrocalcaneal bursitis.     

An MRI-based technique for assessment of lower extremity deformities—reproducibility, accuracy, and clinical application

The hypothesis of this study was that length, torsion, and axis of a leg phantom can be measured accurately and reproducibly by magnetic resonance imaging (MRI) and that this can be applied to patients with leg deformities. Two phantoms and 30 patients (genu varum, n = 15; genu valgum, n = 15) were investigated using an optimized MRI technique. Reference measurements were performed with a micrometer screw and a goniometer. Patient leg length and axis were compared with long radiographs in bipedal stance. Intra- and interobserver reproducibility and accuracy were calculated using the mean absolute difference (MAD) and the 95% confidence interval. In patients, comparisons were done using a paired Student's t-test. MAD, intraobserver MAD, and interobserver MAD were 0.03, 0.03, 0.04 mm (length); 0.98, 1.2, 0.98 degrees (torsion); and 0.18, 0.23, 0.22 degrees (axis), respectively. In patients, leg length was underestimated by MRI (-2.4 +/- 0.7%; 1.9 +/- 0.7 cm; P < 0.001). The hip-knee-ankle angle (HKA) did not show significant differences in varus knees (-0.5 +/- 1.0 degrees ; P > 0.05), while it was significantly underestimated in valgus knees (-3.6 +/- 2.8 degrees ; P < 0.05). The phantom study revealed that leg length, torsion, and axis can be measured accurately and reproducibly by MRI. Although underestimation of leg length and HKA in valgus knees occurred, this optimized MRI technique can be applied to patients with leg deformities.     

Intraoperative seed placement for thoracic malignancy—A review of technique,indications, and published literature

PurposeThis review examines the role of permanent radioactive seed implantation in thoracic malignancy. This technique can be used intraoperatively to provide additional highly localized radiation therapy in cases where optimal oncologic margins are unattainable or to palliate unresectable disease.Methods and materialsRelevant trials were identified through a systematic literature search using Pubmed.ResultsThe intraoperative placement of brachytherapy seeds has been described after sublobar resection for non–small-cell lung cancer (NSCLC), where surgical margins are close or microscopically positive and in the presence of macroscopic residual disease. This brachytherapy technique is currently the focus of a randomized prospective trial in the USA in patients unfit for lobectomy for early-stage NSCLC.ConclusionsThis review summarizes the methods of brachytherapy seed placement and the published experience of brachytherapy implants within the thorax, also examining radiation safety and postoperative dosimetry. This technique has the potential to improve local control with optimal sparing of normal tissue owing to its highly conformal radiotherapy delivery.     

Percutaneous nephrostomy and antegrade ureteral stenting: technique—indications—complications

In this review the technique, indication for and complications of percutaneous nephrostomy (PCN) and antegrade ureter stent insertion are described. In the majority of the cases PCN is performed to relieve urinary obstruction, which can be of benign or malignant nature. Another indication for PCN is for treatment of urinary fistulas. PCN can be performed under ultrasound and/or fluoroscopic guidance, with a success rate of more than 90%. The complication rate is approximately 10% for major and minor complications together and 4–5% for major complications only. Percutaneous antegrade double-J stent insertion usually is performed if retrograde ureter stenting has not been successful. However, especially in malignant obstructions, the success rate for antegrade stenting is higher than for retrograde transvesical double-J stent insertion. In the case of severe infection and bleeding after PCN JJ-stent insertion may be contraindicated so long as there is no sufficient concomitant drainage via a PCN . Lower urinary tract dysfunction should be excluded before stent placement. The complication rate is 2–4%. Consequent stent surveillance with regular stent exchange is mandatory.     

The appended curve technique for deconvolutional analysis —method and validation

Deconvolutional analysis (DCA) is useful in correction of organ time activity curves (response function) for variations in blood activity (input function). Despite enthusiastic reports of applications of DCA in renal and cardiac scintigraphy, routine use has awaited an easily implemented algorithm which is insensitive to statistical noise. The matrix method suffers from the propagation of errors in early data points through the entire curve. Curve fitting or constraint methods require prior knowledge of the expected form of the results. DCA by Fourier transforms (FT) is less influenced by single data points but often suffers from high frequency artifacts which result from the abrupt termination of data acquisition at a nonzero value.To reduce this artifact, we extend the input (i) and response curves to three to five times the initial period of data acquisition (P) by appending a smooth low frequency curve with a gradual taper to zero. Satisfactory results have been obtained using a half cosine curve of length 2-3P. The FTs of the input and response I and R, are computed and R/I determined. The inverse FT is performed and the curve segment corresponding to the initial period of acquisition (P) is retained. We have validated this technique in a dog model by comparing the mean renal transit times of ¹³¹I-iodohippuran by direct renal artery injection to that calculated by deconvolution of an intravenous injection. The correlation was excellent (r=0.97, P0.005).The extension of the data curves by appending a low frequency tail before DCA reduces the data termination artifact. This method is rapid, simple, and easily implemented on a microcomputer. Excellent results have been obtained with clinical data.     

Breast MRI at 7 Tesla with a bilateral coil and T1-weighted acquisition with robust fat suppression: image evaluation and comparison with 3 Tesla

Objectives

To evaluate the image quality of T1-weighted fat-suppressed breast MRI at 7 T and to compare 7-T and 3-T images.

Methods

Seventeen subjects were imaged using a 7-T bilateral transmit-receive coil and 3D gradient echo sequence with adiabatic inversion-based fat suppression (FS). Images were graded on a five-point scale and quantitatively assessed through signal-to-noise ratio (SNR), fibroglandular/fat contrast and signal uniformity measurements.

Results

Image scores at 7 and 3 T were similar on standard-resolution images (1.1?×?1.1?×?1.1-1.6 mm³), indicating that high-quality breast imaging with clinical parameters can be performed at 7 T. The 7-T SNR advantage was underscored on 0.6-mm isotropic images, where image quality was significantly greater than at 3 T (4.2 versus 3.1, P?≤?0.0001). Fibroglandular/fat contrast was more than two times higher at 7 T than at 3 T, owing to effective adiabatic inversion-based FS and the inherent 7-T signal advantage. Signal uniformity was comparable at 7 and 3 T (P?<?0.05). Similar 7-T image quality was observed in all subjects, indicating robustness against anatomical variation.

Conclusion

The 7-T bilateral transmit-receive coil and adiabatic inversion-based FS technique produce image quality that is as good as or better than at 3 T.

Key Points

? High image quality bilateral breast MRI is achievable with clinical parameters at 7 T. ? 7-T high-resolution imaging improves delineation of subtle soft tissue structures. ? Adiabatic-based fat suppression provides excellent fibroglandular/fat contrast at 7 T. ? 7- and 3-T 3D T1-weighted gradient-echo images have similar signal uniformity. ? The 7-T dual solenoid coil enables bilateral imaging without compromising uniformity.     

High-resolution MRI of the wrist and finger joints in patients with rheumatoid arthritis: comparison of 1.5 Tesla and 3.0 Tesla

The goal of this study was to compare magnetic resonance (MR) image quality at different field strengths for evaluating lesions in wrist and finger joints of patients with rheumatoid arthritis (RA) in order to determine whether the higher field strength provides diagnostic gain. The hand mainly affected in 17 RA patients was examined at 1.5 Tesla (T) and 3.0 T with comparable MR imaging (MRI) protocols. MR images were reviewed twice by two experienced radiologists using the Rheumatoid Arthritis MRI Scoring System (RAMRIS) of the OMERACT (Outcome Measures in Rheumatoid Arthritis Clinical Trials) group. Image quality was rated on a five-point scale using Friedmann’s test and Kendall’s W-test for statistical analysis. Image comparison revealed better image quality at higher field strength. Image quality of T1-weighted images was rated 14–22% better at 3.0 T compared with 1.5 T by both readers. Moreover, the rating for the T2-weighted-images acquired at 3.0 T was one point better in the five-point scale used. Inter-reader correlation for image quality, bone erosions/defects, edema and synovitis ranged between 0.6 and 0.9 at 3.0 T and between 0.6 and 0.8 at 1.5 T. Intra-reader correlation for these parameters was high at 0.8–1.0. MRI image quality of RA hands is superior at 3.0 T, while an acceptable image quality is achieved at 1.5 T, which improves the evaluation of extent of bone edema, synovitis and identification of small bone erosions.     

Fluid attenuated inversion recovery (FLAIR) MRI at 7.0 Tesla: comparison with 1.5 and 3.0 Tesla

Purpose

To assess fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) at three field strengths, regarding signal-to-noise ratio (SNR), contrast and signal homogeneity, in order to determine the potential gain and current challenges of FLAIR at ultra-high field strength (7 T).

Methods

FLAIR images of five healthy volunteers (age 24?±?4 years, 4 male) were acquired at 1.5 T, 3 T and 7 T. Image homogeneity and visibility of normal brain structures were evaluated. SNR of grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF) were measured in regions not affected by transmit field heterogeneity.

Results

The SNR (mean ± SD) at 7 T (GM 168?±?15, WM 125?±?11) increased slightly more than proportionally, compared with at 1.5 T (GM 30?±?3, WM 22?±?2) and 3 T (GM 62?±?7, WM 44?±?4). Relative contrast between GM and WM at 7 T (1.35?±?0.07) was slightly less than at 3 T (1.42?±?0.14) or 1.5 T (1.37?±?0.07). Several major fibre bundles became visible at 7 T. One incidentally observed white matter lesion was well visible at all field strengths.

Conclusion

Image homogeneity remains challenging and should be improved by future technical developments. FLAIR imaging at 7 T yields a high SNR,with better contrast for WM substructures and the iron-bearing basal ganglia, and has potential for good conspicuity of WM lesions.